Bladed turbine disks rotate at high speed in an extremely hot environment. Full hoop material is required to resist the centrifugal forces. Any material not contributing to the hoop is dead load, adding weight but not contributing to strength.
A bonded circumferential multi-ring disk is disclosed in copending Application Serial No. (108,171 filed 10-14-87). That arrangement uses multiple circumferential rings near the outer rim of the disk connecting the disk to the blade platform ring. The arrangement provides high strength with low weight, but does not provide for high temperature considerations.
High temperature blading also requires air cooling through the blades with the air passing out openings in the blades into the gas stream. An internal flow path is required to direct the cooling air into the blades.
Rotor assemblies operating in high temperature environments also experience extremely high temperatures in the outer periphery of the rotor assembly. This high temperature causes expansion introducing thermal stress in the disk unless some provision is made to absorb the expansion.